7733 datasheet(606/940 Pages) RENESAS

606 / 940 page

7733 Group User’s Manual

21-58

APPENDIX

Appendix 7. Examples of handling unused pins

The following are examples of handling unused pins.

These are, however, just examples. In actual use, make the necessary adaptations and properly evaluate

performance according to the user’s application.

1. In single-chip mode

Table 1 Examples of handling unused pins in single-chip mode

Handling example

Connect these pins to pin Vcc or Vss via resistors after these

pins are set to the input mode, or leave these pins open after

they are set to the output mode (Note 1).

Leave this pin open.

Connect this pin to pin Vcc.

Connect these pins to pin Vss.

Pins

P0–P8

XOUT (Note 2)

AVcc

AVss, VREF, BYTE

Notes 1: When leaving these pins open after they are set to the output mode, note the following: these pins

function as input ports from reset until they are switched to the output mode by software. Therefore,

voltage levels of these pins are undefined and the power source current may increase while these

pins function as input ports.

Software reliability can be enhanced when the contents of the above ports’ direction registers are

set periodically. This is because these contents may be changed by noise, a program runaway

which occurs owing to noise, etc.

For unused pins, use the shortest possible wiring (within 20 mm from the microcomputer’s pins).

2: This is applied when an external clock is input to pin XIN.

Appendix 7. Examples of handling unused pins

P0–P8

AVss

VREF

BYTE

Vss

AVcc

XOUT

Left open



When setting ports to input mode

VCC

P0–P8

AVss

VREF

BYTE

Vss

AVcc

XOUT

Left open



When setting ports to output mode

Left open

Vcc

Fig. 9 Examples of handling unused pins in single-chip mode

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